Kidney transplantation is the treatment of choice for end stage renal disease. Advances in the treatment of allograft rejection have increased the survival of both patients and their grafts. Nevertheless acute and chronic rejection both continue to hamper graft survival. At one year, about 80% of grafts survive about half survive to 8 years. Failed grafts require dialysis and retransplantation when possible. Prolongation of graft survival effectively increases the supply of organs relative to demand.